For example, JP 2013-218954 A (PTL 1) below discloses an invention relating to a light emitting device including a light source, a wavelength converting member, a light guide plate, and others.
The wavelength converting member is provided between the light source and the light guide plate, and absorbs light having a wavelength of light emitted from the light source and then produces light having a wavelength different therefrom. In the wavelength converting member; for example, a wavelength converting material is encapsulated in a cylindrical receptacle made of glass or the like. The wavelength converting material includes fluorescent pigment, fluorescent dye, quantum dots, or the like. PTL 1 also describes that quantum dots are preferred as the wavelength converting material (see paragraph [0018]). The wavelength converting material absorbs light from a light source, converts it into light having a different wavelength, and emits the converted light. The wavelength converting material is placed in the exact middle between a light entrance plane and a light exit plane of the receptacle as shown in FIG. 2, etc. of PTL 1. Further, as shown in FIG. 2, etc. of PTL 1, the wavelength converting member is placed adjacent to the light source.